Cyclic Combustion Variations in Dual Fuel Partially Premixed Pilot-Ignited Natural Gas Engines

Conference · Wed May 09 00:00:00 EDT 2012 · ASME Proceedings

DOI:https://doi.org/10.1115/ICES2012-81145· OSTI ID:1079587

Srinivasan, K. K. ^[1]; Krishnan, S. R. ^[1]; Qi, Y. ^[2]

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1. Mississippi State Univ., MS (United States). Dept. of Mechanical Engineering
2. Caterpillar, Inc., Peoria, IL (United States)

Dual fuel pilot ignited natural gas engines are identified as an efficient and viable alternative to conventional diesel engines. This paper examines cyclic combustion fluctuations in conventional dual fuel and in dual fuel partially premixed low temperature combustion (LTC). Conventional dual fueling with 95% (energy basis) natural gas (NG) substitution reduces NOx emissions by almost 90%t relative to straight diesel operation; however, this is accompanied by 98% increase in HC emissions, 10 percentage points reduction in fuel conversion efficiency (FCE) and 12 percentage points increase in COVimep. Dual fuel LTC is achieved by injection of a small amount of diesel fuel (2-3 percent on an energy basis) to ignite a premixed natural gas₋air mixture to attain very low NOx emissions (less than 0.2 g/kWh). Cyclic variations in both combustion modes were analyzed by observing the cyclic fluctuations in start of combustion (SOC), peak cylinder pressures (Pmax), combustion phasing (Ca50), and the separation between the diesel injection event and Ca50 (termed "relative combustion phasing" ). For conventional dual fueling, as % NG increases, Pmax decreases, SOC and Ca50 are delayed, and cyclic variations increase. For dual fuel LTC, as diesel injection timing is advanced from 20° to 60° BTDC, the relative combustion phasing is identified as an important combustion parameter along with SoC, Pmax, and CaPmax. For both combustion modes, cyclic variations were characterized by alternating slow and fast burn cycles, especially at high %NG and advanced injection timings. Finally, heat release return maps were analyzed to demonstrate thermal management strategies as an effective tool to mitigate cyclic combustion variations, especially in dual fuel LTC.

• Research Organization: Mississippi State Univ., MS (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: FG36-06GO86025
• OSTI ID: 1079587
• Report Number(s): GO-8602510
• Journal Information: ASME Proceedings, Conference: Proceedings of the ASME 2012 Internal Combustion Engine Division Spring Technical Conference ICES2012, Torino (Italy), 6-9 May 2012
• Country of Publication: United States
• Language: English